This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our Center has two 300 kV JEOL electron cryomicroscopes. They have different cryo-specimen holder design and electron optics. Both of them are equipped with Gatan 4kx4k CCD camera. They can be operated at different temperatures and are evaluated their damage effects for molecular structure determinations.